Prior art devices have used moving retention alteration means, such as a moving heater, to form a chemical substance into a single chemical pulse within a tube. Such apparatus is described by DeFord in U.S. Pat. Nos. 3,043,127 and 3,057,183. Many devices employing moving members for injecting substances onto chromatographic columns are known. All such devices form chemical substances into substantially a single chemical pulse so long as deleterious chromatographic practices resulting in accidental peak splitting are avoided. These prior art devices suffer a disadvantage in that a substance is formed only into a single chemical pulse in a tube.
Another class of prior art devices is the comprehensive multidimensional gas chromatograph of Phillips and Liu. described in U.S. Pat. Nos. 5,196,039 and 5,135,549. These devices suffer a disadvantage in that resistive heaters used to form substances into multiple chemical pulses in a tube have shown a tendency to burn out in practice, and to present difficulties with manufacture.
The present invention solves the aforementioned problems.